The present invention generally relates to security alarm systems which include a plurality of distributed alarm sensors, and which communicate with a system controller at a protected premises. The system controller may communicate with an off-site central station.
The invention particularly relates to a wireless receiver module that is coupled to the system controller and which includes an ability to monitor the operational integrity of the wireless receiver circuitry and distinguish the malfunction of the receiver circuitry.
Over the years, varieties of alarm systems have been developed for reporting event or alarm conditions detected at sensors or transducers distributed about a protected premises. Most frequently, alarm conditions are reported via either hardwired or radio frequency communication links to a system controller at the monitored premises. The system controller, in turn, communicates on a prioritized basis with a central station which is responsive to a number of secured premises. Monitoring staff at the central station respond to the reported alarm and emergency conditions and route appropriate personnel and civil authorities.
Problems inherent in any alarm system are that communication failures can occur at the critical links between the distributed sensors and the system controller and between the system controller and the central station. System controller to central station communications are most typically monitored at the linking phone line connections. Loss of any phone connections to the central station or tampering, are readily detected.
Wireless and hardwired sensor communications to the system controller are most typically monitored by periodically checking the status of each sensor, such as during a supervisory reporting period, e.g. once every 12 or 24 hours. Provisions are not presently available for monitoring the integrity of receiver circuitry that is responsive to any wireless sensors within a system.
It is therefore desirable that either the system controller or an intervening wireless receiver module have an ability to monitor or supervise the operational integrity of the wireless receiver circuitry. The processor at the system controller can thereby be made aware of any defective wireless sensors as well as the operational integrity of the receiver circuitry.
The invention particularly provides a wireless receiver module having such a capability. The receiver module monitors wireless sensor communications (i.e. alarm or event and supervisory messages) in relation to a resettable first timer. The first timer has a period established in statistical relation to the number of wireless sensors in the system and which is presently determined as the ratio of 24 hours to the number of wireless sensors present in the system.
Separate timers monitor conventional supervisory communications from each of the wireless sensors to determine the integrity of each sensor. Failure to detect sensor transmissions within the period of the first timer produces a condition indicative of the failure of the receiver circuitry. Failure to detect normal supervisory communications from each sensor within the period of each of the second timers separately indicates individual sensor failure.